It is known to provide a liquid crystal display apparatus which comprises two liquid crystal panels stacked one on top of the other, and in which the first liquid crystal panel disposed on the viewer side is used as a shutter so as to be able to conceal a portion of the display of the second liquid crystal panel (for example, patent document 1). In such a liquid crystal display apparatus, a secret mode or the like can be achieved by concealing a portion of the display of the second liquid crystal panel.
It is also known to provide a liquid crystal display apparatus which comprises two liquid crystal panels stacked one on top of the other, and in which the liquid crystal panel disposed on the backlight side is used as an open/close means so that good contrast can be obtained regardless of whether the other liquid crystal panel is operated in a reflective mode or a transmissive mode (for example, patent document 2). The backlight-side liquid crystal panel used as the open/close means has the function of allowing the light from the backlight to pass through when the backlight is on, and reflecting the light passed through the other liquid crystal panel when the other liquid crystal panel is operated in the reflective mode with the backlight turned off.
However, in either prior art liquid crystal display apparatus comprising two liquid crystal panels stacked one on top of the other, no attempts have ever been made to operate the two liquid crystal panels in a collaborative manner such that when one liquid crystal panel is turned on, the other liquid crystal panel is turned off, thereby reducing the power consumption of the liquid crystal display apparatus as a whole.
[Patent document 1] Japanese Patent No. 3154498 (FIGS. 1 and 5)
[Patent Document 2] Japanese Unexamined Patent Publication No. H11-258603 (FIG. 1)